Validated at college level, but studies of reliability for younger athletes are ongoing

By James MacDonald, MD, MPH

Reaction time (RT) is commonly prolonged after a sport-related concussion. Besides being a marker for injury (e.g. one of the signs and symptoms of concussion[1]), a rapid reaction time is necessary for protective maneuvers that can reduce the frequency and severity of additional head impacts.

Because prolonged reaction time (RT) is one of the signs of sport-related concussion, a reliable and valid measure of RT is important to a clinician's initial diagnosis and management of concussions, including return to play decisionmaking. Studies show that

impairment of RT is seen post-concussion in college athletes9 and combined high school and college athlete populations.13

for high school athletes, reaction time usually returns to baseline between three and twenty-one days post-concussion. 1-3

boxers show prolonged RT compared to controls several days after symptom resolution.4

prolonged RT is one of the strongest predictors of a longer recovery from concussion and ‘complex' concussions5

Baseline computerized neurocognitive test (CNT) measures of RT have marginal reliability and should not be thought of as the sole measure for evaluating changes in RT post-concussion.7

Novel new test of RT

The Sideline-Dropstick test is a novel clinical test of reaction time using a device similar to one used in high school physics experiments and was initially developed by a group from the University of Michigan. 8,9,15

Studies show that it:

is a valid and reliable RT measure for college athletes.10

has good short- and long-term test-retest and inter-rater reliability.10,11

correlates with sport-related protective response (such as, for example, the time it takes for a soccer player to raise their hands to protect the head from a rapidly approaching ball);6

is intrinsically motivating (e.g. the motivation to do well on the test arises from within the athlete because it is intrinsically rewarding. 12

correlates with computerized neurocognitive test measures of RT in baseline testing of college athletes.8

appears to be sensitive to the effects of concussion and distinguished concussed and non-concussed athletes with similar sensitivity and specificity to other commonly used concussion assessment tools.15

Given its simplicity, low cost and minimal time requirement, should be considered a viable component of the sports medicine provider's multifaceted concussion assessment battery.15

It should be noted that validation of the Sideline-Dropstick test in high school athletes is ongoing, but has not yet been done in middle school and younger athletic populations.14

[2]

Make Your Own

To administer the Sideline Dropstick you will need to build a dropstick and use a random number generator (there are several random number generator applications available for free download on smartphones)

Here's how to make a dropstick:

Supplies

7/16" dowel rod

Rubber ice
hockey puck

Friction tape (what one would use for ‘grip tape' to tape a tennis racquet. Should be a light color. I have used "Tourna" Grip Tape, green colored, in my research).

Standard push pin/thumbtack

Power drill with 3/8 inch bit

Wood saw and/or Leatherman tool

Wood glue

Superglue

Felt tip marker (a black "Sharpie" with a fine point works well; you need one with ink that is easy to see against the friction tape)

Instructions

Using the drill and 3/8 inch bit, drill into the puck, making sure not to drill all the way through.

Remove the rubber shavings from the hole, put in a little wood glue, and then shove the dowel into the glue-filled hole.

Wipe off the excess. (Sometimes you may need to shave down the very end of the dowel rod to get a good fit; a Leatherman's knife blade can be used for this).

Allow the glued pieces to dry.

Measure off 85 cm of dowel rod from the surface of the puck, and using the saw cut off the remainder of the dowel rod in excess of the 85 cm. A push pin should be easily inserted into the top of the dowel rod. We coat the push pin in superglue when we are putting the pin in to ensure it will not loosen easily.

Wrap the dowel rod from the base of the puck up to the top of the dowel rod in the friction tape.

To mark the device, the surface of the hockey puck represents ‘zero.' Measure off 1 cm and ½ cm marks all the way to 80 cm. See the video above for details.

Administering the Sideline-Dropstick test

To obtain a baseline, have the athlete sit comfortably next to a desk using their dominant (writing) hand in the position demonstrated in the video. They are given one practice trial.

The test administrator then administers 8 recorded trials dropping the stick after a 2 to 8 second pause (use the random number generator each time to determine the time interval to drop).

Record the distance dropped for each one of the eight trials. A simple equation can be used to convert the distance to time in milliseconds:8 RT (ms) = 1000x √(2 x distance in cm)/(980cm/s2). See the video for more details.

Compare to baseline

The sideline-dropstick test may be administered on the sideline, though in our experience, we will commonly take the potentially concussed athlete to the training room to perform testing in a more controlled, less distracting environment than the sideline. We will compare their average performance on 8 drops with their baseline performance. We consider this measure of RT, along with the patient's performance on SCAT3[3] and BESS[4] testing when determining whether the patient may have sustained a concussion or not. Impairment of RT (a performance worse than baseline) should be considered a potentially significant marker of having sustained a concussion.

Jim MacDonald is a physician specializing in pediatric sports medicine at Nationwide Children's Hospital in Columbus, Ohio and Clinical Assistant Professor of Pediatrics and Family Medicine at the Ohio State University's School of Medicine and Nationwide. An Associate Editor of the Clinical
Journal of Sport Medicine, MacDonald is a Fellow of the American College of
Sports Medicine, and is a member of MomsTEAM Institute's Board of Advisors.
He earned both his Bachelor's and Medical degrees from Harvard University, and his Masters in Public Health from The Ohio State University. He did his pediatric sports medicine training at Boston Children's Hospital and was previously Team Physician at the University of California, Santa Cruz before coming to Columbus.

As
a clinical researcher Dr. MacDonald has received grant funding from
the American Medical Society for Sports Medicine (AMSSM) and Nationwide
Children's Hospital (NCH). He has experience leading multidisciplinary
teams in a variety of research projects investigating the diagnosis and
management of pediatric sport-related concussions and in the use of
patient-reported outcome measures (PROMs) in the evaluation of pediatric
musculoskeletal injuries. His publications and interests also include
work on Exercise-Deficit Dysfunction (EDD) in children, a precursor to
childhood obesity. Jim is the married father of ten-year old sports-active twins, a boy and a girl.

Sideline-Dropstick Test: A Simple Measure of Reaction Time For Use In Identifying Possible Concussion

Teaser image:

Teaser text:

A simple, easy-to-construct and easy-to-use dropstick device to measure reaction time, which is impaired after concussion, could help sideline personnel identify athletes to remove from play because of possible concussion, and in concussion assessment and management.